The present invention relates generally to surface treatment of ceramics, and more particularly to a surface treatment for magnetic recording heads using plasma immersion ion implantation and deposition.
The use and development of plasma- and ion-assisted material modification processes to selectively alter the structure and physicochemical properties of surfaces has received increasing attention in recent years. In particular, ion implantation as a nonequilibrium process provides a unique means for developing surface layers with novel compositions and microstructures that are otherwise difficult or impossible to obtain. In conventional ion implantation, a beam of energetic ions extracted from a plasma source is accelerated toward the surface to be implanted. The ions impinging on the solid surface at high energy become buried at depths typically in the range of 0.01 to 1 microns (.mu.m), thus resulting in the modification of the atomic composition and lattice structure of the near-surface region without affecting the surface roughness, dimensional tolerances, and bulk material properties, as in the case of other high-temperature vacuum coating techniques. Metallurgical reactions that occur with ion implantation, such as a solid solution of implant element, generation of dislocations and point defects, alteration of crystallinity (amorphization), precipitation of second phases and compound formation and changes in the chemical composition and stress-strain state, can produce a significant hardening and strengthening effect on a thin surface layer which, in turn, may greatly enhance the fatigue life, oxidation resistance, and tribological properties, such as friction and wear, of a wide range of base materials used in various industrial and medical prostheses applications.
Since ion implantation is a line-of-sight operation, component manipulation and beam rastering are required in order to achieve spatial uniformity in treatment. This limits the size of the component that can be implanted (target) and imposes a need for special fixturing. Furthermore, the necessity to provide sufficient heat sinks and masking to inhibit excessive heating and sputtering of the target introduces additional complexity to the process. Plasma source ion implantation is a non-line-of-sight implantation technique of greater processing throughput which circumvents the aforementioned drawbacks and restrictions. The target is immersed in a plasma and repetitively pulse-biased to a high negative voltage relative to the plasma potential. A plasma sheath forms around the target and the ions accelerate through the electric field of the sheath bombarding all exposed areas of the target simultaneously. Although this process provides an effective means for achieving enhanced surface properties, it is limited to implanting species that are gaseous at room temperature, e.g., nitrogen and oxygen.
It is apparent from the foregoing that unique surface properties can be obtained with the plasma immersion ion implantation technique. One of the most rapidly emerging technologies where significant advancements in materials processing can be achieved with such a technique is magnetic recording media. As magnetic hard disk drives have evolved to higher storage densities, the head-disk spacing (flying height) has been reduced to the present state-of-the-art of .about.0.1 .mu.m. Remarkably smaller spacings, in the range of 0.025 to 0.05 .mu.m, are predicted for the near future in view of the technology trend for much higher storage densities. Operation at such low flying heights enhances the intermittent contact of the magnetic recording head with the disk, thus resulting in friction build-up and accelerated wear damage of both head and disk surfaces. Although significant progress has been made toward the development of durable thin films for hard disks, surface modification of magnetic recording heads, or other ceramic articles, for enhancing the friction and wear characteristics at the head-disk interface has received relatively less attention.
Accordingly, an object of the present invention is to provide a method for improving the friction and wear properties of magnetic recording heads and other ceramic articles.
Another object of the present invention is to provide a method for enhancing the smoothness and hardness of magnetic recording heads and other ceramic articles.
Yet another object of the present invention is to provide a low temperature and short duration surface treatment for enhancing the smoothness, hardness, friction and wear properties of magnetic recording heads and other ceramic articles.
Still another object of the present invention is to provide a surface treatment for magnetic recording heads and other ceramic articles that can be carried out using a wide variety of solid metal, solid nonmetal and gaseous species.
A further object of the present invention is to provide a surface treatment for magnetic recording heads and other ceramic articles, yielding a combination of phases attainable by deposition and phases attainable by ion implantation with atomic interfacial mixing.
Another object of the present invention is to provide a surface treatment for magnetic recording heads and other ceramic articles wherein original tolerances are maintained.
Still another object of the present invention is to provide a surface treatment for modifying the surface resistivity of magnetic recording heads and other ceramic articles.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the claims.